Mnemonic 1 — Laws of Chemical Combination (in order)

"Can David Make Good Atoms?"

• Conservation of mass — Lavoisier (1789)
• Definite proportions — Proust (1799)
• Multiple proportions — Dalton (1803)
• Gaseous volumes — Gay-Lussac (1808)
• Avogadro's Law (1811)

Mnemonic 2 — Temperature Dependence of Concentration Terms

"My Molality Mole-fraction Mass-percent Never Pops" (temperature-INDEPENDENT ones)

• Molality
• Mole fraction
• Mass percent
• Normality? — NO! Normality involves volume → temperature-DEPENDENT.
• ppm

Or simply: "Mass-based = Temperature-independent" (molality, mole fraction, mass %, ppm use mass).

Mnemonic 3 — Mole Conversion Hub — "MoNey VaN"

At the center is Moles. From moles you go to:

• Number of particles (× Nₐ)
• Volume at STP (× 22.4 L)
• mass (× molar mass)
• Normality / equivalents (× n-factor)

Mnemonic 4 — Empirical Formula Steps — "DMSD"

• Divide each % by atomic mass → get ratios
• Minimum ratio → divide all by smallest
• Simplify to whole numbers (multiply by 2, 3… if needed)
• Done — that's your empirical formula!

Visual Hook — Avogadro's Number

$6.022 \times 10^{23}$ — remember "602 sixes" = 6·02·2 or think "6 + 02 + 2 = ??? No!" just remember: $602.2 \times 10^{21}$. Easier: it is approximately $6 \times 10^{23}$ for quick calculations.